Microwave imaging of bone was introduced several years ago with the idea of its potential application as an alternative non-ionizing diagnostic method of bone health. The suggested applications attempted to restore the complete permittivity map of the bone and surrounding tissue. Due to the well-known complexity and poor spatial resolution of the standard microwave imaging setup used in these studies, no clinically applicable results have been generated to date.
In osteoporosis, bone mass decreases and pore size increases. The lost bone mass is replaced by a mixture of yellow bone marrow, with a dielectric constant that is five times less than the value for normal trabecular bone at 900 MHz, and fat, with a dielectric constant that is two times less than the value for normal trabecular bone at 900 MHz. According to the present invention, the decrease in the dielectric constant generates significantly different scattering and/or reflection of an RF signal passing through the bone. Therefore, all that may be required for osteoporosis detection is tracking of such a signal along the path through the bone instead of restoring the complete permittivity map, as previously attempted.
Accordingly, the method and device of the present invention apply a different technical approach to osteoporosis detection. Instead of a typical microwave imaging setup, the present invention comprises a simple transmitter-receiver setup including but not limited to a modern RFID reader with an on-skin reader antenna and a number of on-skin passive RFID tags surrounding the bone in the form of an array. The novel design of the present invention eliminates the need for a custom beamforming network and will reduce both the cost and the complexity by an order of magnitude.